<!DOCTYPE html>
<html>
<head>
  <style>
    @keyframes spin {
      0% { transform: rotate(0deg); }
      100% { transform: rotate(360deg); }
    }

    .box {
      width: 100px;
      height: 100px;
      background-color: red;
      animation: spin 1s linear infinite;
    }
  </style>
</head>
<body>
<div class="box"></div>
</body>
</html>
